Karachi: At least four persons were killed and 7 others injured in a string of attacks by militants targeting liberal political parties ahead of the May 11 polls.

A convoy of an independent candidate came under attack in Sibi, killing 4 people. Seven people were injured when militants attacked the offices of Pakistan Muslim League-Nawaz (PML-N) and National Party in other parts of the Balochistan province.

Police said that despite enhanced security for candidates, militants had attacked a convoy of Sardar Sarfaraz Domki and Dostain Domki candidates for provincial and national Assembly seats in Karak area of Sibi district.

"Four people were killed in the attack when militants opened fire on an election rally. The candidates had taken out," one official said. In another incident, militants hurled a hand grenade at the office of Jamiatul Ulema-e-Islam (Ideological) in Deba area of Quetta.

Police said two people were injured in the attack, the assailants however managed to escape. Police official Imran Baloch said that militants had also thrown hand grenades at the office of PML-N leader General (retd) Abdul Qadir in Kharan town.

Baloch said five PML-N workers were injured in the attack. The blast also damaged the electoral office of PML-N. Militants also targeted the electoral office of National Party in Mach town in the same method, he added. "Three workers were injured in the attack," he said.